PROJECT SUMMARY Epidemiological studies consistently report that one of the most reliable predictors of whether an adolescent or young adult will use drugs is whether his or her friends use drugs. Social learning theories of drug use propose that members of a social group model drug use behaviors and other members subsequently imitate those behaviors. Furthermore, members of the social group selectively reinforce/punish the drug use of others depending on the norms established by that group. Until recently, experimental studies examining the predictions of social learning theories have been limited because of ethical (human studies) or technical (animal studies) constraints limiting the modeling and imitation of illicit drug use. Over the last five years, we have developed and validated custom-built, IACUC-approved, operant conditioning chambers that permit two (or more) rats to intravenously self-administer drugs simultaneously, side-by-side, in the same chamber. Using these chambers, we reported that drug self-administration could either be increased or decreased depending on the behavior of a partner (i.e., whether the partner was also self-administering drugs). In this competing renewal of our research project grant (R01DA031725, Social Influences on Drug-Seeking Behavior), we will significantly expand the use of these chambers to advance our understanding of the social factors that contribute to substance abuse and its treatment. In Aim 1, we will determine whether a partner's (1) amount of responding or (2) amount of drug intake (i.e., level of intoxication) is responsible for the effects of social contact on drug self-administration by separately manipulating the schedule and dose maintaining responding in the partner. In Aim 2, we will examine the role of the reinforcing stimulus in determining the effects of social contact on drug intake by manipulating the reinforcer (cocaine, heroin, food) for both rats of a social dyad. In Aim 3, we will test how social contact influences the efficacy of a pharmacological intervention to reduce cocaine intake by manipulating whether a partner has access to cocaine over the course of treatment. In Aim 4, we will determine the effects of (1) social reinforcement and (2) social punishment on drug intake by giving or removing access to a partner contingent on drug self-administration. In all studies, both male and female rats will be used, and sex will be examined as a biological variable. The long-term goal of this project is to identify factors that more accurately predict drug use within social groups and to identify treatment interventions that incorporate the social environment to curtail drug use.